<!DOCTYPE html>
<html lang="zh-cn">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>javascript 阶段</title>
    <style>
        div {
            width: 100px;
            height: 100px;
            border: 1px solid #ccc;
        }
    </style>
</head>
<body>

    <div>1</div>
    <div class="box">2</div>
    <div id="demo">3</div>



    <!-- 引入公共的JS文件 -->
    <script src="./common/util.js"></script>
    <script>
        // 调用方法1：
        var el = _("div");
        console.log(el);

        var el = _(".box");
        console.log(el);

        var el = _("#demo");
        console.log(el);
        
    </script>
</body>
</html>